I don't know about an in depth explanation - I am pretty shell shocked these days (working too much).THe key is wait until the coating is setup a little bit - the same time that it starts to suck up the pigment, is about the same time you start polishing with a trowel. Usually you splash water with a big brush at the same time - you can see it has to be quite firm.
You are in Canada - the plaster/stucco store will have a bag of "diamond' veneer finish. I am not even suggesting this is a fresco plaster - but it will give you a simple example of the desired effect.
It is thought that the frescoes of pompeii and india were polished after painting, with a spoon like tool. They wanted smooth walls because of all the dust. The ISraeli frescoist also polishes his fresco after painting with a smooth glass bottle. Ilia is on record of cringing at this process. Maybe the Italian limes are too soft for this. I have never tried it with a painted surface but have many times with plaster. I remember the architect caressing the silky, cool, freshly polished surface and smiling. It truly is as sensuous as the finest skin.
